梅雨季刚过，户外电表箱里的PBT接线端子脆化了，维修师傅用螺丝刀一碰就掉渣。供电局批量召回，改性厂老板盯着退回的端子发呆——PBT本身易水解，但配方里没加抗水解剂，端羧基在湿热环境下不断催化分子链断裂，等于给塑料装了个自毁程序。
工程塑料的水解，是水分子拿着小剪刀，一节节剪断你的分子链。
本文由长期经营塑料原料及助剂的宁波市科隆新材料有限公司整理，牌号与批次信息以实际供货渠道为准。
抗水解剂速查总表：三大体系一页看完
抗水解剂不是什么广谱防潮神药“防潮药”，它有自己的适用谱系。碳化二亚胺类是当之无愧的主力，专门收拾聚酯、聚酰胺这类“见水就软”的料；封端剂、扩链类助剂则从另一头补位。下面这张表把主流体系的代表品种、关键参数和添加比例列清楚，选型先对号入座。
| 体系 | 代表品种 | 关键参数 | 典型制品 | 添加比例 |
|---|
| 碳化二亚胺类（CDI） | 单体型CDI、聚合型PCD | 含N=C=N活性基团，耐温150-250℃ | PET/PBT瓶片、纤维、汽车件 | 0.5%-2.0% |
| 封端/扩链辅助类 | 环氧ADR、噁唑啉类 | 与羧基/羟基反应封端 | 回收PET增粘、PBT改性 | 0.1%-0.5% |
| 复合抗水解体系 | CDI+抗氧剂168/626 | 封端+加工稳定协同 | PA66、PBT户外湿热件 | 总0.6%-2.5% |
注：表中有效成分和添加量为参考，水解稳定性以双85老化实测和官方TDS为准。选型逻辑一句话：先看基材有没有酯键、酰胺键，再看使用环境是不是高温高湿，两条都占，就该上抗水解剂。
图1 抗水解剂——工程塑料在湿热环境下的分子链防护屏障
水解是场链式反应，封端就是给分子链“上锁”
这位主角，是工程塑料的抗洪战士。宁波市科隆新材料有限公司长期经营各类塑料助剂及改性原料，覆盖国内外多个品牌货源，在碳化二亚胺类抗水解剂、封端剂、扩链剂等聚酯聚酰胺专用助剂上有稳定的供货渠道。而抗水解剂这个品类，本质上是工程塑料在湿热环境下的“分子链锁”——PET、PBT、PA、TPU这些材料的主链上挂着酯键和酰胺键，水分子一旦钻进去，在热的助攻下就会不断把这些键剪断，剪断后生成的端羧基又会催化下一次水解，越剪越快，材料于是从韧性材料一步步退化成发黏、变脆的废品。
抗水解剂就像给工程塑料穿了件雨衣，水汽进不来，分子链才断不了。
碳化二亚胺类（CDI）的高明之处，在于它不跟水分子硬刚，而是去收拾“帮凶”。分子链被剪断后露出的端羧基，是催化水解链式反应的发动机。CDI分子上那个活泼的N=C=N基团，专找端羧基反应，把它“中和”掉，链式反应的引信就被拔掉了。这叫“封端”——不是把水挡在门外，而是让断了的链头不再继续往下断。
端羧基是水解链式反应的引信，CDI干的就是拔引信这活——0.5%-2%看着不多，拔掉的却是整锅料的自毁开关。
这里有个常见误区：有人以为加了抗水解剂就万事大吉，加工前不用烘料。错。抗水解剂管的是“使用过程中”的长期耐水解，管不了“进挤出机那一刻”料里自带的水分。PA、PC、PET加工前照样要按规程烘干，否则料筒里的水会在260℃以上瞬间水解，封端剂救都救不回来。
哦，你拿没封端的PBT去做户外电表箱？梅雨季一过就粉，这叫裸奔上岗。
逐品种速查：单体型反应快，聚合型耐迁移
碳化二亚胺也分单体型和聚合型，听起来玄乎，其实差别就在“跑得快还是站得稳”。下面逐个讲清楚定位和选型信号。
封端省下来的每一克端羧基，都是梅雨季不脆裂的底气。
单体型碳化二亚胺（如含芳香族N=C=N结构的液体或低熔点品种）：分子量小、扩散快，能迅速渗透到熔体里捕捉端羧基，适合回收PET瓶片增粘、PBT短流程改性。优点是起效快、用量省；缺点是小分子易迁移、加工挥发略大，厚壁和长期热水场景要留意析出。选它的信号：回收料增粘、薄膜纤维类快周转加工。
供货提示：碳化二亚胺类抗水解剂科隆新材有货源，每批附有效成分含量，公斤级试样支持先做湿热老化对比。
聚合型碳化二亚胺（PCD）：把多个CDI基团聚到一条主链上，分子量大、不迁移、耐抽出，特别适合汽车发动机周边、热水壶、咖啡机、PBT连接器这类要长期泡在热水或湿热环境里的件。缺点是价格比单体型高、分散需要一点剪切。选它的信号：要求长期耐热水、耐抽出、低析出的中高端制品。
环氧类扩链/封端剂（ADR）：严格说它是扩链剂，但在回收PET体系里常和CDI搭着用——ADR靠环氧基团同时接羧基和羟基，把断链两头重新长起来，CDI负责把多余羧基封掉，一加一大于二。选它的信号：回收PET瓶片增粘、纤维回用。
热水壶、咖啡机、汽车冷却系统，这些天天见水的件，都得靠抗水解剂兜底。
替代对照：进口CDI能不能换？先看这张表
做PBT、PET改性的采购常问：进口碳化二亚胺能不能用国产替代？答案是可以，但要认清楚自己卡在哪一步。通用回收PET增粘场景，国产CDI的活性值、添加量差距已经不大；但在汽车级、长期耐热水1000小时以上的严苛场景，进口聚合型PCD在低挥发、批次一致性上仍有积累。下面这张表列清替代方向和切换前提。
| 原用进口方向 | 典型应用 | 可对标方案 | 切换前提 |
|---|
| 莱茵化学Stabaxol系列CDI | PET/PBT通用抗水解 | 国产单体型/聚合型CDI | 小试对比端羧基值变化、85℃×85%RH×1000h力学保留率 |
| 巴斯夫Joncryl ADR扩链剂 | 回收PET增粘 | 国产环氧ADR对标品 | 对比熔体强度、IV（特性粘度）回升幅度 |
| 汽车级聚合型PCD | PA66发动机周边件 | 国产聚合型CDI | 对比130℃水煮1000h后冲击保留、析出/喷霜 |
| 纤维级液体CDI | PET纺丝增粘 | 国产液体CDI | 对比纺丝稳定性、可纺性、黄变ΔE |
表中所列是应用方向参考，并不意味着性能直接划等号。替代顺序老规矩：小试→平行对比→客户书面确认→小批量→放量，任何一步卡壳就停下来查。
抗水解剂替代要做双85湿热老化对比，科隆新材提供公斤级碳化二亚胺试样时随附有效成分含量，客户可以直接跑85℃/85%RH×1000h平行测试，数据达标再放量。
水解发脆别怪料，先查原料有没有预干燥、封端量够不够，别上来就甩锅给树脂厂。
行业场景速查：谁在天天跟水打交道
同样是加抗水解剂，做家电外壳和做汽车热管理件，考核的湿热周期差着量级。下面这张表按行业拆解，帮你快速定位方案。
| 行业 | 典型制品 | 客户最先问的参数 | 推荐方案 | 认证要求 |
|---|
| 汽车 | 节气门、水室、传感器外壳 | 85℃×85%RH×1000h后力学保留率 | 聚合型PCD 0.5%-1.5%+抗氧 | IATF 16949、耐冷却液 |
| 家电 | 咖啡机、热水壶、电熨斗座 | 100℃水煮500h不发黏 | 聚合型CDI+168/626 | 食品接触GB 4806、LFGB |
| 电子电器 | PBT连接器、线轴 | 焊锡耐热+湿热绝缘保持 | CDI+阻燃+抗氧体系 | UL黄卡、RoHS |
| 包装纤维 | 回收PET瓶片、涤纶短纤 | 特性粘度IV回升、纺丝稳定 | 单体型CDI/ADR 0.1%-0.3% | 食品接触GB 4806.7 |
| 光伏 | 封装胶膜配套、接线盒 | 湿热双85老化1000h | 耐水解PBT/PPA体系 | IEC 61215、UL |
举个真实场景：做汽车水室，客户要求85℃×85%RH×1000小时后拉伸保留率不低于80%。这种单靠烘料根本兜不住，必须上聚合型CDI并把端羧基值压下来，同时搭配高温抗氧剂扛住注塑和使用时的热老化。
添加量与搭配要点：三条铁律记牢
抗水解剂的用量不是拍脑袋，而是跟着端羧基值和湿热等级走。下面三条是行业里反复验证过的搭配逻辑。
做PET/PBT/PA的湿热件，先把碳化二亚胺加上，再谈别的配方。
◆ 通用PBT/PET改性：单体型CDI 0.5%-1.0%，配合168/626加工抗氧，总添加0.7%-1.2%，够应付一般湿热仓储和使用。
◆ 汽车级长期耐热水：聚合型PCD 1.0%-2.0%，专攻端羧基，配高温抗氧，应对双85或130℃水煮这类严苛工况。
◆ 回收PET增粘：环氧ADR 0.1%-0.5%为主，必要时补0.2%-0.5%单体型CDI封残酸，IV回升和封端两头抓。
搭配要点还有三条：一是抗水解剂和加工前烘干是“前后接力”关系，烘干管加工、CDI管使用，谁都替代不了谁；二是CDI与酸性物质（如部分阻燃体系析出物）可能反应失效，配方里有酸性组分要重新核算用量；三是回收料端羧基值波动大，每批回料建议先测端羧基值再定CDI添加量，别一刀切。
遇水不慌，封端有方。
水解：封端为先。
加工与合规红线：这几个坑别踩
抗水解剂用不对，轻则没效果，重则析出喷霜。下面这张表把加工环节的关键参数和做错的后果列出来。
| 环节 | 参考值 | 做错的后果 |
|---|
| 原料预干燥 | PET 120-140℃×4-6h，PA 80-100℃×4-8h | 带水进机→料筒内瞬间水解，CDI白加 |
| 挤出温度 | PBT 230-250℃，PET 260-280℃ | 温度过高→CDI提前消耗、制品黄变 |
| CDI预混 | 与树脂粉高速混合3-5分钟，均匀分散 | 分散不均→局部封端不足、批次波动 |
| 加工停留时间 | 避免螺杆死角和过长停留 | 停留过久→封端剂提前反应失效 |
| 储存条件 | 密封干燥、温度<30℃、湿度<60% | 受潮吸湿→活性下降、结块 |
合规红线同样不能松：接触热水、食品的制品，抗水解剂及其迁移物要符合GB 4806系列或FDA、LFGB相关条款；汽车件要符合IATF 16949和各主机厂的湿热耐久规范；出口欧盟需满足REACH。批次COA、迁移测试报告要随货索取归档。
FAQ：配方和采购最常问的五个问题
Q1：国产抗水解剂能不能替代进口料？
可以分场景看。通用回收PET增粘、普通PBT改性，批次稳定的国产CDI性能差距已经很小；但汽车级长期耐热水、低析出的聚合型PCD，进口在批次一致性和低挥发控制上仍有优势。稳妥做法是先拿公斤级样品做平行测试，对比端羧基值变化、湿热老化后力学保留率和析出表现，过了再小批量放量。对照样品可联系科隆新材按公斤级索取，随批次有效成分数据一并比对。
Q2：加了抗水解剂，料还要不要烘干？
必须烘。这是两件事：烘干负责把树脂里自带的游离水去掉，防止加工时料筒内水解；CDI负责使用过程中长期抑制水解。很多人加了CDI就偷懒不烘干，结果注塑出来的件还是发脆——那是加工阶段水解的，封端剂管不着。
Q3：抗水解剂加越多越好吗？
不是。CDI过量会有残留游离物，反而带来析出、喷霜、影响力学和表面光泽；而且价格不便宜，加多了纯属浪费。正确做法是先测原料端羧基值，按目标湿热寿命反推添加量，通常落在0.5%-2%区间，别盲目堆料。
Q4：它和扩链剂ADR是一回事吗？
不完全是。ADR靠环氧基团把断链两头重新接长，主攻“提分子量”；CDI靠与端羧基反应，主攻“终止水解”。回收PET体系里两者常搭档：ADR把链接长，CDI把多余羧基封掉，效果比单用一个更稳。
Q5：怎么判断我的料需不需要加抗水解剂？
看两条：一是基材是不是PET、PBT、PA、TPU这类含酯键/酰胺键的；二是制品使用环境是不是长期高温高湿、接触热水或冷却液。两条都占，基本要加；如果只是干燥室内常温用的普通PP/ABS，通常用不上。
选型三步清单：照着做不踩坑
◆ 第1步·定工况：搞清楚制品是不是长期高温高湿、是否接触热水/冷却液，预期湿热老化周期（如双85×1000h）要多高，再决定用单体型还是聚合型CDI。
◆ 第2步·测酸值：先测原料和回料的端羧基值，按目标寿命反推CDI添加量（0.5%-2%），并和抗氧剂、阻燃剂做兼容性核算。
◆ 第3步·核认证：按最终用途确认食品接触、汽车、UL、REACH等合规要求，索取批次COA、迁移测试报告并归档。
湿热环境里，分子链不断才是硬道理
抗水解剂主要用于PET、PBT、PA、TPU等易水解树脂，通过捕捉端羧基终止水解链式反应。科隆新材供应碳化二亚胺类抗水解剂，可提供有效成分含量和湿热老化参考数据；户外电表、汽车冷却系统、热水管等湿热场景可推荐对应用量，公斤级试样支持先做85℃/85%RH老化对比。
前年，一家做PBT电表端子的厂被供电局召回——梅雨季过后端子脆化。科隆新材给他们推荐了碳化二亚胺类抗水解剂，添加量约1%，寄了公斤级样品。客户做了85℃/85%RH×1000小时测试，冲击强度保留率从原来的约40%提升到约80%。重新供货后，第二年梅雨季没再出现批量脆化，供电局的订单从一个省扩到了三个省。
户外件的配方里，抗水解剂加了吗？
声明：本文涉及的品牌、商标及产品名称权归各自原厂所有。本文为第三方选材知识分享，文中提及的牌号、参数、价格、认证及应用案例仅供参考，具体以各生产企业官方最新资料及批次检测报告为准。本文不构成任何采购或投资建议，读者据此操作风险自担。
Just after the plum rain season, the PBT terminals in outdoor electric meter boxes became brittle, and the repair technician could crumble them with a screwdriver. The power supply bureau issued a mass recall, and the boss of the modification factory stared blankly at the returned terminals—the PBT itself is prone to hydrolysis, but the formula did not include an anti-hydrolysis agent, and the terminal carboxyl groups continuously catalyze chain breaks in the humid and hot environment, effectively installing a self-destruct program in the plastic.
The hydrolysis of engineering plastics is like water molecules holding tiny scissors, cutting your molecular chains segment by segment.
This article is compiled by Ningbo Kolong New Materials Co., Ltd., which has long been engaged in the business of plastic raw materials and additives. The grade and batch information are subject to the actual supply channels.
Quick Reference Table of Water-Resistant Agents: Overview of the Three Major Systems on One Page
Anti-hydrolytic agents are not some kind of universal moisture-proof miracle 'moisture-proof drug'; they have their own applicable spectrum. Carbodiimide compounds are the undisputed main force, specially dealing with materials like polyester and polyamide that 'soften upon contact with water'; end-capping agents and chain-extending auxiliaries make up from the other side. The table below clearly lists the representative products, key parameters, and addition ratios of mainstream systems, so you can first match your choice accordingly.
| system | Representative varieties | Key parameters | Typical products | Add ratio |
|---|
| Carbodiimide (CDI) | Monolithic CDI, Polymeric PCD | Contains N=C=N active groups, resistant to temperatures of 150-250℃ | PET/PBT bottle flakes, fibers, automotive parts | 0.5%-2.0% |
| End-capping/Chain-extension Auxiliary Class | Epoxy ADR, oxazoline class | End-capping by reaction with carboxyl/hydroxyl groups | Recycled PET viscosity enhancement, PBT modification | 0.1%-0.5% |
| Composite anti-hydrolysis system | CDI Antioxidant 168/626 | Sealing end, stable processing collaboration | PA66, PBT outdoor humid heat components | Total 0.6%-2.5% |
Note: The active ingredients and additive amounts in the table are for reference; hydrolysis stability should be based on actual double 85 aging tests and the official TDS. Selection logic in one sentence: first check whether the substrate has ester or amide bonds, then see if the usage environment is high temperature and high humidity; if both conditions are met, a hydrolysis inhibitor should be used.
Figure 1 Hydrolysis Inhibitor — Molecular Chain Protective Barrier of Engineering Plastics in Humid and Hot Environments
Hydrolysis is a chain reaction, and end-capping is like 'locking' the molecular chain.
This main character is the flood-fighting warrior of engineering plastics. Ningbo Kolon New Materials Co., Ltd. has long been engaged in various plastic additives and modified raw materials, covering multiple domestic and international brands. It has stable supply channels for polyester and polyamide-specific additives such as carbodiimide hydrolysis stabilizers, end-cappers, and chain extenders. The hydrolysis stabilizer category, in essence, is the 'molecular chain lock' for engineering plastics in hot and humid environments—materials like PET, PBT, PA, and TPU have ester and amide bonds on their main chains. Once water molecules penetrate, with the aid of heat, they continuously break these bonds. The resulting terminal carboxyl groups then catalyze the next hydrolysis, accelerating the process. Gradually, the material degrades from a tough material into a sticky, brittle waste product.
Water-resistant agents are like putting a raincoat on engineering plastics; moisture can't get in, so the molecular chains won't break.
The brilliance of carbonyldiimidazole (CDI) lies in the fact that it doesn’t confront water molecules head-on, but rather deals with the 'accomplice.' The carboxyl end groups exposed after the molecular chain is cleaved act as the engine for the catalytic hydrolysis chain reaction. The reactive N=C=N group on the CDI molecule specifically reacts with these end carboxyl groups, 'neutralizing' them, and thus the fuse of the chain reaction is removed. This is called 'end-capping' — not to block water at the door, but to prevent the broken chain ends from continuing to break further.
The terminal carboxyl group is the fuse for the hydrolytic chain reaction. CDI's job is exactly to pull the fuse—0.5%-2% seems like a small amount, but what it pulls out is the self-destruct switch of the entire batch.
Here is a common misconception: some people think that adding an anti-hydrolysis agent solves everything, so there's no need to dry the material before processing. Wrong. Anti-hydrolysis agents ensure long-term hydrolysis resistance during use, but they can't deal with the moisture already present in the material the moment it enters the extruder. PA, PC, and PET still need to be dried according to the proper procedure before processing; otherwise, the water in the barrel will instantly hydrolyze the material at temperatures above 260°C, and end-capping agents won't be able to save it.
Oh, you used unsealed PBT for the outdoor electricity meter box? After the rainy season passes, it will turn powdery; this is called going to work naked.
Quick check by variety: Monomer type responds quickly, polymer type resists migration
Carbodiimide is also divided into monomeric and polymeric types. It sounds complicated, but the difference is basically whether it 'runs fast or stands firm.' Below, we'll explain the positioning and selection signals one by one.
Every gram of terminal carboxyl group saved from sealing is the confidence that it won't crack during the rainy season.
Monomeric carbodiimides (such as liquids or low-melting types containing aromatic N=C=N structures): they have small molecular weights and diffuse quickly, allowing them to rapidly penetrate the melt and capture terminal carboxyl groups. They are suitable for increasing the viscosity of recycled PET flakes and short-process modification of PBT. The advantages are fast action and low dosage; the disadvantages are that small molecules can migrate easily and volatilize slightly during processing, so attention should be paid to precipitation in thick-walled products and long-term hot water applications. Signals for choosing them: increasing viscosity of recycled materials, fast-turnover processing of films and fibers.
Supply Notice: Carbonized diimide-type anti-hydrolysis agents are available from Cologne New Materials, with each batch accompanied by the active ingredient content. Kilogram-scale samples support preliminary wet heat aging comparison tests.
Polymeric Carbodiimide (PCD): Multiple CDI groups are polymerized onto a single main chain, resulting in a high molecular weight, non-migratory, and extract-resistant compound, particularly suitable for parts around car engines, electric kettles, coffee machines, and PBT connectors that need to be immersed in hot water or humid environments for long periods. The drawback is that it is more expensive than monomeric types and requires some shear for dispersion. Signals to choose it: products that require long-term resistance to hot water, extraction, and low leaching in mid-to-high-end applications.
Epoxy-type chain extender/terminal agent (ADR): Strictly speaking, it is a chain extender, but in the recycled PET system it is often used together with CDI—ADR uses its epoxy groups to react with both carboxyl and hydroxyl groups, reconnecting the broken chain ends, while CDI is responsible for capping the excess carboxyl groups, making the combination more effective than either alone. The signals for choosing it: increases viscosity for recycled PET bottle flakes and fiber reuse.
Electric kettles, coffee machines, car cooling systems—these parts that see water every day all rely on hydrolysis inhibitors as a safeguard.
Alternative comparison: Can imported CDI be replaced? Take a look at this table first
Common questions in PBT and PET modification procurement: Can imported carbodiimide be replaced with domestic products? The answer is yes, but you need to understand exactly where the bottleneck is. In general recycled PET viscosity enhancement scenarios, the difference in activity value and dosage between domestic CDI and imports is minimal; however, in automotive-grade applications or demanding scenarios requiring long-term heat resistance in water for over 1000 hours, imported polymeric PCD still has advantages in low volatility and batch consistency. The table below clarifies the replacement directions and prerequisites for switching.
| Original imported direction | Typical applications | Benchmark solution | Switch premise |
|---|
| Rhein Chemie Stabaxol Series CDI | General hydrolysis-resistant for PET/PBT | Domestic Monomer/Polymer CDI | Preliminary test comparing changes in terminal carboxyl value and mechanical retention rate under 85°C × 85% RH × 1000 h |
| BASF Joncryl ADR Chain Extender | Recycle PET thickening | Domestic epoxy ADR benchmark product | Compare melt strength and IV (intrinsic viscosity) recovery range |
| Automotive-grade polymerized PCD | PA66 engine peripheral parts | Domestic polymer-based CDI | Comparison of impact retention and precipitation/spraying after boiling at 130°C for 1000 hours |
| Fiber-grade liquid CDI | PET spinning thickening | Domestic liquid CDI | Comparison of spinning stability, spinnability, and yellowing ΔE |
The applications listed in the table are for reference and do not imply a direct equivalence in performance. The substitution sequence follows the usual procedure: small-scale test → parallel comparison → written confirmation from the customer → small batch → mass production. If any step encounters a problem, stop and investigate.
When replacing the hydrolysis inhibitor, a comparison test under dual 85°C/85% RH damp heat aging should be conducted. When Cologne New Materials provides kilogram-level samples of carbodiimide, the effective component content is included. The customer can directly carry out parallel testing at 85°C/85% RH for 1000 hours, and if the data meets the standards, production can be scaled up.
Don't blame the material for becoming brittle after hydrolysis. First, check whether the raw materials were pre-dried and whether the end capping amount is sufficient. Don't immediately pass the blame to the resin manufacturer.
Industry Scene Quick Lookup: Who Deals with Water Every Day
Even when adding anti-hydrolysis agents, the wet heat cycle requirements are orders of magnitude different between appliance housings and automotive thermal management components. The table below breaks it down by industry to help you quickly identify solutions.
| Industry | Typical products | The parameters the customer asked about first | Recommended plan | Certification requirements |
|---|
| Car | Throttle body, water chamber, sensor housing | Mechanical retention rate after 85℃ × 85% RH × 1000h | Aggregate-type PCD 0.5%-1.5% antioxidant | IATF 16949, coolant resistant |
| Home appliances | Coffee maker, electric kettle, iron base | 500 hours of boiling in 100℃ water without becoming sticky | Polymeric CDI 168/626 | Food contact GB 4806, LFGB |
| Electronics and electrical appliances | PBT connector, spool | Solder heat resistance, insulation retention under damp heat | CDI flame-retardant antioxidant system | UL Yellow Card, RoHS |
| Packaging fiber | Recycling PET bottle flakes and polyester staple fiber | Intrinsic viscosity (IV) recovery, stable spinning | Monotherapy CDI/ADR 0.1%-0.3% | Food Contact GB 4806.7 |
| photovoltaic | Encapsulation film sets, junction boxes | Damp heat double 85 aging 1000h | Hydrolysis-resistant PBT/PPA system | IEC 61215, UL |
Here's a real-world scenario: producing an automotive water chamber, the customer requires that after 85°C × 85% RH × 1000 hours, the tensile retention rate should not be less than 80%. This can't be achieved by just drying the material; a polymeric CDI must be used and the terminal carboxyl value must be reduced, while also pairing with high-temperature antioxidants to withstand the thermal aging during injection molding and usage.
Dosage and Key Points of Combination: Remember the Three Iron Rules
The amount of hydrolysis inhibitor is not decided arbitrarily; it follows the terminal carboxyl value and the wet-heat grade. The following three points are combinations repeatedly verified in the industry.
For hot and humid parts made of PET/PBT/PA, first add dicyandiamide, then discuss other formulations.
◆ General PBT/PET modification: Monomer-type CDI 0.5%-1.0%, combined with 168/626 processing antioxidants, total addition 0.7%-1.2%, sufficient to cope with general humid and hot storage and usage.
◆ Automotive-grade long-term heat-resistant water: Polymeric PCD 1.0%-2.0%, specially targeting terminal carboxyl groups, paired with high-temperature antioxidants, designed to withstand harsh conditions such as dual 85 or 130°C boiling.
◆ Recycling PET increase in viscosity: Mainly 0.1%-0.5% epoxy ADR, if necessary, add 0.2%-0.5% monomer-type CDI to cap residual acid, focusing on both IV recovery and end-capping.
There are three more key points for matching: First, the hydrolysis inhibitor and pre-processing drying have a 'relay' relationship—drying before processing and using CDI during processing are irreplaceable; second, CDI may react with acidic substances (such as some flame-retardant system precipitates) and fail, so if there are acidic components in the formulation, the amount needs to be recalculated; third, the carboxyl value of recycled materials fluctuates greatly, so it is recommended to measure the carboxyl value of each batch before determining the CDI dosage, rather than applying a one-size-fits-all approach.
Stay calm when faced with water, and there is a proper way to seal the end.
Hydrolysis: end-capping comes first.
Processing and Compliance Red Lines: Avoid These Pitfalls
If the anti-hydrolysis agent is used incorrectly, at best it will have no effect, at worst it will cause frosting. The table below lists the key parameters of the processing steps and the consequences of mistakes.
| link; segment; part | Reference value | The consequences of doing wrong |
|---|
| Raw material pre-drying | PET 120-140℃ × 4-6h, PA 80-100℃ × 4-8h | Add water into the machine → Instant hydrolysis in the barrel, CDI added white |
| Extrusion temperature | PBT 230-250℃, PET 260-280℃ | Excessive temperature → premature CDI consumption, product yellowing |
| CDI Premix | Mix with resin powder at high speed for 3-5 minutes until evenly dispersed | Uneven dispersion → insufficient local sealing, batch fluctuations |
| Processing dwell time | Avoid screw dead spots and excessively long residence time | Excessive stay → Fuser agent reacts prematurely and fails |
| Storage conditions | Seal and keep dry, temperature <30℃, humidity <60% | Absorbs moisture → reduced activity, caking |
Compliance red lines must not be relaxed: products that come into contact with hot water and food, hydrolysis-resistant agents and their migration substances must comply with GB 4806 series or relevant FDA and LFGB regulations; automotive parts must meet IATF 16949 and the wet-heat durability specifications of each OEM; exports to the EU must comply with REACH. Batch COA and migration test reports must be requested and archived along with the goods.
FAQ: The Five Most Frequently Asked Questions About Recipes and Purchasing
Q1: Can domestic hydrolysis inhibitors replace imported materials?
It can be viewed according to different scenarios. For general PET recycling adhesion enhancement and regular PBT modification, the performance gap of stable batch domestic CDI is already very small; however, for automotive-grade long-term heat-resistant water and low-exudation polymeric PCD, imports still have advantages in batch consistency and low volatility control. A prudent approach is to first take kilogram-level samples for parallel testing, comparing the changes in terminal carboxyl value, mechanical retention after humid heat aging, and exudation performance, and only after passing these tests move to small-scale production. Reference samples can be requested in kilogram quantities from Cologne New Material, and batch effective component data should be compared together.
Q2: After adding the anti-hydrolysis agent, does the material still need to be dried?
Drying is a must. These are two separate things: drying is responsible for removing the free water naturally present in the resin to prevent hydrolysis inside the barrel during processing; CDI is responsible for long-term inhibition of hydrolysis during use. Many people get lazy and skip drying after adding CDI, and as a result, the injection-molded parts still turn out brittle—that is due to hydrolysis during processing, which the end-capping agent cannot prevent.
Q3: Is it better to add more water-resistant agent?
No. Excessive CDI leaves residual free matter, which leads to precipitation, frosting, influencing, and surface gloss; Moreover, the price is not cheap, and adding too much is pure waste. The correct approach is to first measure the carboxyl value at the raw material end, then calculate the amount based on the target damp heat life, usually in the 0.5%-2% range. Don't blindly pile up material.
Q4: Is it the same as chain extender ADR?
Not exactly. ADR relies on epoxy groups to reconnect both ends of a broken chain, focusing on "increasing molecular weight"; CDI relies on reactions with end carboxygroups, focusing on "terminating hydrolysis." In recycled PET systems, these two are common partners: ADR extends the link, CDI seals excess carboxyl groups, which is more stable than using just one product.
Q5: How do I tell if my material needs anti-hydrolysis agents?
Look at two points: first, whether the substrate contains ester or amide bonds like PET, PBT, PA, TPU; second, whether the product is used in a long-term high temperature and humidity, contact with hot water or coolant. If both are met, you basically need to add it; If it's just ordinary PP/ABS used at room temperature in the drying room, it usually won't be needed.
Three-Step Selection Checklist: Follow this to avoid pitfalls
◆ Step 1 · Determine operating conditions: Determine whether the product is in high temperature and humidity for a long time, whether it comes into contact with hot water/coolant, and how long the expected damp heat aging cycle (e.g., dual 85 × 1000 hours) should be, then decide whether to use monomer or polymer CDI.
◆ Step 2 · Acid Value Measurement: First, measure the end carboxyl values of raw materials and return materials, then calculate the CDI addition amount (0.5%-2%) based on the target lifespan, and calculate compatibility with antioxidants and flame retardants.
◆ Step 3 · Nuclear Certification: Confirm compliance requirements for food contact, automotive, UL, REACH, etc. by end use, request batch COA and migration test reports, and archive them.
In humid and hot environments, continuous molecular chains are the key
anti-hydrolytic agents are mainly used in easily hydrolyzable resins such as PET, PBT, PA, and TPU, terminating the hydrolysis chain reaction by capturing the carboxyl group at the end. Kolon New Materials supplies diamide carbide anti-hydrolytic agents, which can provide reference data for active ingredient content and damp heat aging; Recommended application amounts for outdoor meters, automotive cooling systems, hot water pipes, etc., with kilogram-level samples supporting 85°C/85% RH aging comparison.
Two years ago, a factory producing PBT meter terminals was recalled by the power bureau—terminals became brittle after the rainy season. Kolon New Materials recommended diamidide carbide anti-hydrolysis agents to them, with an added amount of about 1%, and sent kilogram-level samples. The customer conducted a 1000-hour test at 85°C/85% RH× increasing the impact strength retention rate from about 40% to about 80%. After resupply, there was no further batch brittleness during the rainy season the following year, and the power supply bureau's orders expanded from one province to three provinces.
Did the outdoor parts formula include anti-hydrolytic agents?
Statement: The brands, trademarks, and product names mentioned in this article belong to their respective original manufacturers. This article is a third-party material selection knowledge sharing. The grades, parameters, prices, certifications, and application cases mentioned are for reference only. Please refer to the latest official information and batch test reports of each manufacturer. This article does not constitute any procurement or investment advice; readers are responsible for any risks in their actions
